Load Data to R Shiny

In this blog post, we will explore the different ways to load data into R Shiny applications.

1. Uploading data from the user interface:

One of the easiest ways to load data into a Shiny application is to allow users to upload their own data files. Shiny provides the fileInput function, which allows users to select and upload their files from the local machine. The uploaded files can be accessed using the input object in the server function.

ui <- fluidPage(
  fileInput("file1", "Choose CSV File",
            accept = c("text/csv",
                       "text/comma-separated-values,
                       .csv"))
)

server <- function(input, output) {
  data <- reactive({
    infile <- input$file1
    if (is.null(infile)) {
      return(NULL)
    }
    read.csv(infile$datapath, header = TRUE)
  })
}

2. Loading data from a URL:

Another way to load data into a Shiny application is to directly load data from a URL. This is useful if the data is hosted on a server and needs to be accessed by multiple users. The read.table or read.csv function can be used to load data from a URL.

server <- function(input, output) {
  data <- reactive({
    url <- "http://example.com/data.csv"
    read.csv(url)
  })
}

3. Loading data from a database:

Shiny applications can also load data directly from a database. This is useful when dealing with large datasets that cannot be easily loaded into memory. The DBI and RMySQL packages can be used to establish a connection to a database and query data. Check out this post for how to learn to work with SQLite.

library(DBI)
library(RMySQL)

con <- dbConnect(MySQL(), user = "username", password = "password", 
                 host = "localhost", dbname = "database")

server <- function(input, output) {
  data <- reactive({
    query <- "SELECT * FROM tablename"
    dbGetQuery(con, query)
  })
}

4. Loading data from a file on the server:

Finally, data can also be loaded directly from a file on the server where the Shiny application is running. This is useful when the data file is too large to be uploaded by the user or when the data needs to be refreshed periodically.

server <- function(input, output) {
  data <- reactive({
    file <- "/path/to/data.csv"
    read.csv(file)
  })
}

In conclusion, there are several ways to load data into a Shiny application, including uploading data from the user interface, loading data from a URL, loading data from a database, and loading data from a file on the server. The method used depends on the type and size of data and the specific requirements of the application.

This post first appeared on rshiny.blog.